The present disclosure relates to an image forming apparatus, a temperature control method for use in a fixing device, and a non-transitory computer-readable recording medium storing a program for controlling an image forming apparatus.
Conventionally, there have been known image forming apparatuses such as copiers, printers, facsimiles that operate based on the electrophotography. A typical image forming apparatus includes a fixing device. The fixing device applies a pressure onto a sheet on whose surface a toner image has been transferred, while applying heat thereto. This allows the toner image to be fixed to the sheet. A typical fixing device includes a pair of rotators, namely a fixing roller and a pressure roller. A heat source, such as a heater, is embedded in the fixing roller. The pressure roller is disposed to face the fixing roller, and the outer circumferential surface thereof is pressed against and contacted with the fixing roller.
The fixing device performs a temperature control to maintain the fixing roller at a predetermined fixing temperature to maintain a fixable state during an image forming period. The power consumption for heating the fixing device accounts for 70% to 80% of the power consumption of the image forming apparatus. To attain the power saving by reducing the power consumption of the image forming apparatus, the fixing device, during an image non-forming period, performs the temperature control to maintain the fixing roller at a wait temperature, which is lower than the fixing temperature. Specifically, during the temperature control, when the fixing roller becomes lower than the wait temperature, the heat source is operated to heat it, and when the fixing roller becomes equal to or higher than the wait temperature, the heat source is stopped to stop heating. It is noted that the wait temperature is a temperature arbitrarily set in a range from a temperature during a non-heating period to the fixing temperature. For example, the wait temperature is set to such a temperature of the fixing roller that can quickly be raised to the fixing temperature for the image formation by operating the heat source in response to an input of an image forming instruction.
In addition, to attain the power saving, when image data for printing is not input to the image forming apparatus during a predetermined time period, the fixing device performs a temperature control to change the temperature of the fixing roller from the fixing temperature to the wait temperature. As a technology related to the temperature control, there is known, for example, a technology to reduce the time required to start printing the first sheet, by changing the temperature of the fixing roller from the wait temperature to the fixing temperature while scanning the image data on the photoconductor drum during returning from the wait state. As another technology related to the temperature control, there is known, for example, a technology to determine whether or not an initialization process is necessary immediately after the apparatus is powered on, and upon determining that the initialization process is necessary, warm up the fixing device.